Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2007. / Includes bibliographical references (p. 201). / The last decade has been a period of fundamental transformations for the US airline industry and has caused many carriers to make significant changes in their operational strategies. The traditional US network or "Legacy" carriers have had to deal with many new challenges including the devastating effects of 9/11, increased competition from low-cost airlines and increased volatility in fuel prices, to name a few. These setbacks have pushed many carriers into a financial crisis. In fact, four out of the six major airlines in the United States filed for bankruptcy protection between 2001 and 2005. In the midst of this crisis, these traditional carriers have had to concentrate on reducing their unit costs and improving their productivity levels in order to survive. The goal of the thesis is to examine to what extent these changes have led to a convergence in terms of unit costs and productivity levels between the Legacy carriers and their low-cost counterparts. Specifically we analyze and break down unit costs and productivity measures into their underlying components in order to identify what is driving change in the industry. We compare the different results at various levels of detail, including aggregate industry group trends, individual airline results and fleet-level based results comparing wide-body to narrow-body aircraft. We find that there are both qualitative and quantitative signs of convergence in several different categories in which LCCs have traditionally held a competitive advantage. These include unit costs excluding fuel and transport-related expenses, labor unit costs and employee wage productivity. On the Legacy side, the key forces driving improved efficiency have been dramatic labors cuts and higher stage lengths. / (cont.) The former has been achieved by utilizing the bankruptcy while the latter results from the shifting of capacity towards international markets. On the LCC side we find that a significant increase in labor wages resulting from increased staff seniority has been the main source of losses in certain productivity results. Despite these signs of convergence, our fleet-level based analysis also showed that LCCs still retain a significant competitive advantage when isolating narrow-body fleets which are usually flown in the domestic US markets. / by Gerassimos Tsoukalas. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1991. / Includes bibliographical references (leaves 66-67). / by Sen-Hao Lai. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2002. / Includes bibliographical references (leaves 66-68). / by Mark Alexander Kepets. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1988. / Includes bibliographical references. / by John Charles Brewer. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 179-181). / For a variety of missions, vision-based navigation and similar architectures provide the advantage of detailed measurements for a fraction of the size and complexity of ground-based imagers. This thesis provides a simple navigation algorithm using no more than a visual centroid measurement to enable in-situ inspection of space objects. This work evaluates those inspection maneuvers using the Synchronize Position Hold Engage Reorient Experimental Satellites, known as SPHERES. Evaluation of hardware performance was done using data from the International Space Station, in concert with ground-based simulations. Ultimately, this work is in preparation for future experimentation using the VERTIGO vision-navigation payload for SPHERES. The first step presented is an analysis of the measurement capabilities of the SPHERES system and the predicted performance of the VERTIGO system. Using this analysis it is shown that tests run using the former system are applicable to the latter in terms of accuracy, precision, and observability. The second step is an analysis of the tests run on the Space Station, a comparison to those predicted by simulation, and an extension of those results to simulations of more complex maneuvers. Further, a determination of the robustness of the control to disturbances is also performed. Finally, this thesis reflects on the technical and programmatic challenges of developing the VERTIGO payload. From these challenges, lessons are drawn which may guide future developers and program managers, particularly in the university engineering environment. / by Michael Christopher O'Connor. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2002. / Includes bibliographical references (leaves 97-99). / by Melvin Michael Henry. / S.M.

Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. Thesis. 1965. Sc.D. / Bibliography: leaves 178-192. / Sc.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1990. / Includes bibliographical references (leaves 124-135). / by Simon Andrew Collins. / M.S.

Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics. Thesis. 1968. M.S. / MICROFICHE COPY ALSO AVAILABLE IN AERO LIBRARY. / One blank page inserted. / Bibliography: leaves 84-85. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2005. / "June 2005." / Includes bibliographical references (p. 77-79). / Artificial gravity provided by short radius centrifugation is considered a promising countermeasure to the deleterious physiological effects of microgravity during long-duration space flight. We investigated the feasibility of dual countermeasures to address space flight deconditioning of the musculoskeletal and cardiovascular systems, by combining centrifugation with lower-body exercise. The exercise device is a small stair-stepper with constant resistance provided by dampers beneath each foot, and is the first such device to be used in centrifuge studies. We modified the existing centrifuge to support the additional stresses due to exercise and added following structural elements: support struts on the rotation shaft, a redesigned footplate to which the exercise device was mounted, and horizontal support beams. We also added a sliding mattress with linear ball bearings on rails, so that the subject's body can move up and down while stepping. Design changes and exercise feasibility were validated by having subjects exercise during centrifugation at 23 rpm. We measured heart rate, blood pressure, forces on the feet, and knee deflection due to Coriolis accelerations, for up to four subjects. As expected, heart rate and blood pressure did increase normally with exercise on the centrifuge, relative to when not exercising. However, both heart rate and systolic blood pressure were higher for exercise on the non-spinning centrifuge than on the spinning centrifuge, attributable to the necessity of pulling against the stair-stepper's dampers in order to exercise while lying supine. Approximately half the subject's weight was exerted on the footplate when not exercising. / (cont.) This was expected: since the subject's head was at zero radius and thus at 0-g radially, the 100% artificial gravity gradient along the body's longitudinal axis gave an average effective gravity of about 0.5 g. More pressure (up to 80% body weight) was exerted when the subject was stair-stepping. The measured lateral deflection of the knee during normal stair-stepping and knee bend exercises increased up to three inches compared to deflections in a non-rotating environment. This issue must be further addressed to determine if stair-stepping or knee bend exercises are to be used safely in artificial gravity. / by Jessica Leigh Edmonds. / S.M.